Nanozymes With Osteochondral Regenerative Effects: An Overview of Mechanisms and Recent Applications.

With the discovery of the intrinsic enzyme-like activity of metal oxides, nanozymes garner significant attention due to their superior characteristics, such as low cost, high stability, multi-enzyme activity, and facile preparation. Notably, in the field of biomedicine, nanozymes primarily focus on disease detection, antibacterial properties, antitumor effects, and treatment of inflammatory conditions. However, the potential for application in regenerative medicine, which primarily addresses wound healing, nerve defect repair, bone regeneration, and cardiovascular disease treatment, is garnering interest as well. This review introduces nanozymes as an innovative strategy within the realm of bone regenerative medicine. The primary focus of this approach lies in the facilitation of osteochondral regeneration through the modulation of the pathological microenvironment. The catalytic mechanisms of four types of representative nanozymes are first discussed. The pathological microenvironment inhibiting osteochondral regeneration, followed by summarizing the therapy mechanism of nanozymes to osteochondral regeneration barriers is introduced. Further, the therapeutic potential of nanozymes for bone diseases is included. To improve the therapeutic efficiency of nanozymes and facilitate their clinical translation, future potential applications in osteochondral diseases are also discussed and some significant challenges addressed.

Advances in 3D Printing of Highly Bioadaptive Bone Tissue Engineering Scaffolds.

The number of patients with bone defects caused by trauma, bone tumors, and osteoporosis has increased considerably. The repair of irregular, recurring, and large bone defects poses a great challenge to clinicians. Bone tissue engineering is emerging as an appropriate strategy to replace autologous bone grafting in the repair of critically sized bone defects. However, the suitability of bone tissue engineering scaffolds in terms of structure, mechanics, degradation, and the microenvironment is inadequate. Three-dimensional (3D) printing is an advanced additive-manufacturing technology widely used for bone repair. 3D printing constructs personalized structurally adapted scaffolds based on 3D models reconstructed from CT images. The contradiction between the mechanics and degradation is resolved by altering the stacking structure. The local microenvironment of the implant is improved by designing an internal pore structure and a spatiotemporal factor release system. Therefore, there has been a boom in the 3D printing of personalized bone repair scaffolds. In this review, successful research on the preparation of highly bioadaptive bone tissue engineering scaffolds using 3D printing is presented. The mechanisms of structural, mechanical, degradation, and microenvironmental adaptations of bone prostheses and their interactions were elucidated to provide a feasible strategy for constructing highly bioadaptive bone tissue engineering scaffolds.

[In vitro biological evaluation of PEGylated poly(glycerol sebacate)/ß-TCP-coating modified magnesium alloy].

PURPOSE: To prepare PEGS/ß-TCP modified magnesium alloy (PEGS/ß-TCP/MZG) membranes by forming a glycolated poly(sebacate)/ß-tricalcium phosphate (PEGS/ß-TCP) coating on the surface of magnesium-zinc-gadolinium alloy (MZG) membranes, and to evaluate the osteogenic induction activity and immunomodulatory properties of PEGS/ß-TCP/MZG using the material extract medium. METHODS: PEGS/ß-TCP coating was prepared on the surface of MZG by solvent method, and the PEGS/ß-TCP/MZG membrane was fabricated and compared with PEGS/ß-TCP and MZG to examine the morphology, composition, and hydrophilicity. The amount of magnesium ions released and the pH value of the materials were tested after 3 days of immersion. The cell viability and osteogenic differentiation of MC3T3 cells induced by extract medium were investigated by CCK-8 assay, ALP and mineralized nodule staining. The cell viability and polarization of RAW cells induced by extract medium were then investigated. The expression of macrophage-secreted cytokines was examined by PCR analysis. GraphPad Prism 9.0 software package was used for statistical analysis. RESULTS: PEGS/ß-TCP/MZG membranes with PEGS/ß-TCP coating tightly embedded with MZG were successfully fabricated, and the material had good hydrophilicity. The results of degradation experiments indicated that the PEGS/ß-TCP coating effectively slowed down the degradation rate of MZG, leading to a lower pH value and concentration of Mg2+ ion in the extract medium of PEGS/ß-TCP/MZG group. The results of in vitro cell experiments showed that PEGS/ß-TCP/MZG had no significant effect on the proliferation activity of both MC3T3-E1 and macrophages. PEGS/ß-TCP/MZG significantly enhanced the expression of ALP and mineralized nodule staining in MC3T3-E1. Although there was no significant difference in macrophage polarization pattern between PEGS/ß-TCP and PEGS/ß-TCP/MZG groups, PEGS/ß-TCP/MZG further reduced inflammation based on the immunomodulation of PEGS/ß-TCP coating related TNF-α expression and increased osteogenesis related TGF-ß expression. CONCLUSIONS: MZG membrane modified by PEGS/ß-TCP may provide a new material option for the development of bone tissue engineering.

Photocurable 3D-printed PMBG/TCP biphasic scaffold mimicking vasculature for bone regeneration.

Mesoporous bioglass (MBG) with excellent osteointegration, osteoinduction, and biodegradability is a promising material for bone regeneration. However, its clinical application is hindered by complex processing and a lack of personalization, low mechanical strength, and uncontrollable degradation rate. In this study, we developed a double-bond-functionalized photocurable mesoporous bioglass (PMBG) sol that enabled ultrafast photopolymerization within 5 s. By further integrating nanosized tricalcium phosphate (TCP) particles through three-dimensional (3D) printing technology, we fabricated personalized and highly porous PMBG/TCP biphasic scaffolds. The mechanical properties and degradation behavior of the scaffolds were regulated by varying the amount of TCP doping. In vitro and in vivo experiments verified that PMBG/TCP scaffolds slowly released SiO44- and Ca2+, forming a vascularized bone regeneration microenvironment within the fully interconnected pore channels of the scaffold. This microenvironment promoted angiogenesis and accelerated bone tissue regeneration. Overall, this work demonstrates the solution to the problem of complex processing and lack of personalization in bioglass scaffolds, and the developed PMBG/TCP biphasic scaffold is an ideal material for bone regeneration applications with broad clinical prospects.

Photocurable 3D-Printed PMBG/TCP Scaffold Coordinated with PTH (1-34) Bidirectionally Regulates Bone Homeostasis to Accelerate Bone Regeneration.

Bone defect repair remains a major clinical challenge that requires the construction of scaffolds that can regulate bone homeostasis. In this study, a photo-cured mesoporous bioactive glass (PMBG) precursor is developed as a tricalcium phosphate (TCP) agglomerant to obtain a double-phase PMBG/TCP scaffold via 3D printing. The scaffold exhibits multi-scale porous structures and large surface areas, making it a suitable carrier for the loading of parathyroid hormone (PTH) (1-34), which is used for the treatment of osteoporosis. In vitro and in vivo results demonstrate that PMBG/TCP scaffolds coordinated with PTH (1-34) can regulate bone homeostasis in a bidirectional manner to facilitate bone formation and inhibit bone resorption. Furthermore, bidirectional regulation of bone homeostasis by PTH (1-34) is achieved by inhibiting fibrogenic activation protein (FAP). Thus, PMBG/TCP scaffolds coordinated with PTH (1-34) are viable materials with considerable potential for application in the field of bone regeneration and provide an excellent solution for the design and development of clinical materials.

Double-network hydrogel enhanced by SS31-loaded mesoporous polydopamine nanoparticles: Symphonic collaboration of near-infrared photothermal antibacterial effect and mitochondrial maintenance for full-thickness wound healing in diabetes mellitus.

Diabetic wound healing has become a serious healthcare challenge. The high-glucose environment leads to persistent bacterial infection and mitochondrial dysfunction, resulting in chronic inflammation, abnormal vascular function, and tissue necrosis. To solve these issues, we developed a double-network hydrogel, constructed with pluronic F127 diacrylate (F127DA) and hyaluronic acid methacrylate (HAMA), and enhanced by SS31-loaded mesoporous polydopamine nanoparticles (MPDA NPs). As components, SS31, a mitochondria-targeted peptide, maintains mitochondrial function, reduces mitochondrial reactive oxygen species (ROS) and thus regulates macrophage polarization, as well as promoting cell proliferation and migration, while MPDA NPs not only scavenge ROS and exert an anti-bacterial effect by photothermal treatment under near-infrared light irradiation, but also control release of SS31 in response to ROS. This F127DA/HAMA-MPDA@SS31 (FH-M@S) hydrogel has characteristics of adhesion, superior biocompatibility and mechanical properties which can adapt to irregular wounds at different body sites and provide sustained release of MPDA@SS31 (M@S) NPs. In addition, in a diabetic rat full thickness skin defect model, the FH-M@S hydrogel promoted macrophage M2 polarization, collagen deposition, neovascularization and wound healing. Therefore, the FH-M@S hydrogel exhibits promising therapeutic potential for skin regeneration.

Multifunctional 3D-printed bioceramic scaffolds: Recent strategies for osteosarcoma treatment.

Osteosarcoma is the most prevalent bone malignant tumor in children and teenagers. The bone defect, recurrence, and metastasis after surgery severely affect the life quality of patients. Clinically, bone grafts are implanted. Primary bioceramic scaffolds show a monomodal osteogenesis function. With the advances in three-dimensional printing technology and materials science, while maintaining the osteogenesis ability, scaffolds become more patient-specific and obtain additional anti-tumor ability with functional agents being loaded. Anti-tumor therapies include photothermal, magnetothermal, old and novel chemo-, gas, and photodynamic therapy. These strategies kill tumors through novel mechanisms to treat refractory osteosarcoma due to drug resistance, and some have shown the potential to reverse drug resistance and inhibit metastasis. Therefore, multifunctional three-dimensional printed bioceramic scaffolds hold excellent promise for osteosarcoma treatments. To better understand, we review the background of osteosarcoma, primary 3D-printed bioceramic scaffolds, and different therapies and have a prospect for the future.

3D bioprinting tumor models mimic the tumor microenvironment for drug screening.

Cancer is a severe threat to human life and health and represents the main cause of death globally. Drug therapy is one of the primary means of treating cancer; however, most anticancer medications do not proceed beyond preclinical testing because the conditions of actual human tumors are not effectively mimicked by traditional tumor models. Hence, bionic in vitro tumor models must be developed to screen for anticancer drugs. Three-dimensional (3D) bioprinting technology can produce structures with built-in spatial and chemical complexity and models with accurately controlled structures, a homogeneous size and morphology, less variation across batches, and a more realistic tumor microenvironment (TME). This technology can also rapidly produce such models for high-throughput anticancer medication testing. This review describes 3D bioprinting methods, the use of bioinks in tumor models, and in vitro tumor model design strategies for building complex tumor microenvironment features using biological 3D printing technology. Moreover, the application of 3D bioprinting in vitro tumor models in drug screening is also discussed.

Osteoclast-Driven Osteogenesis, Bone Remodeling and Biomaterial Resorption: A New Profile of BMP2-CPC-Induced Alveolar Bone Regeneration.

This bedside-to-bench study aimed to systematically investigate the value of applying BMP2-loaded calcium phosphate cement (BMP2-CPC) in the restoration of large-scale alveolar bone defects. Compared to deproteinized bovine bone (DBB), BMP2-CPC was shown to be capable of inducing a favorable pattern of bone regeneration and bone remodeling accompanied by active osteoclastogenesis and optimized biomaterial resorption when applied in reconstructive periodontally accelerated osteogenic orthodontics (PAOO) surgery. To verify the regulatory role of osteoclasts in the BMP2-CPC-induced pattern of bone regeneration, in vitro and in vivo studies were designed to elucidate the underlying mechanism. Our results revealed that osteoclasts played a multifaceted role (facilitating osteogenesis, bone remodeling and biomaterial resorption) in the BMP2-CPC-induced bone regeneration. Osteoclasts contributed to the osteogenic differentiation of mesenchymal stem cells (MSCs) by secreting calcium ions, CTHRC1 and PDGF-B. Moreover, the increased osteoclasts promoted the remodeling of new bone and BMP2-CPC resorption, leading to a harmonized replacement of biomaterials with mature bone. In conclusion, the in vitro and in vivo experimental results corresponded with the clinical results and showed the optimized properties of BMP2-CPC in activating osteoclast-driven bone regeneration and remodeling, thus indicating the highly promising prospects of BMP2-CPC as an ideal therapeutic for alveolar bone defects.

A Nanozyme-Immobilized Hydrogel with Endogenous ROS-Scavenging and Oxygen Generation Abilities for Significantly Promoting Oxidative Diabetic Wound Healing.

Non-healing wound is a common complication of diabetic patients associated with high morbidity and mortality. Engineered therapeutic hydrogels have enviable advantages in tissue regeneration, however, they are suboptimal for the healing of diabetic wounds characterized by reactive oxygen species (ROS) accumulation and chronic hypoxia. Here, a unique biological metabolism-inspired hydrogel, for ameliorating this hostile diabetic microenvironment, is presented. Consisting of natural polymers (hydrazide modified hyaluronic acid and aldehyde modified hyaluronic acid) and a metal-organic frameworks derived catalase-mimic nanozyme (ε-polylysine coated mesoporous manganese cobalt oxide), the engineered nanozyme-reinforced hydrogels can not only capture the endogenous elevated ROS in diabetic wounds, but also synergistically produce oxygen through the ROS-driven oxygen production ability. These fascinating properties of hydrogels protect skin cells (e.g., keratinocytes, fibroblasts, and vascular endothelial cells) from ROS and hypoxia-mediated death and proliferation inhibition. Diabetic wounds treated with the nanozyme-reinforced hydrogels highlight the potential of inducing the macrophages polarization from pro-inflammatory phenotype (M1) to anti-inflammatory subtype (M2). The hydrogel dressings demonstrate a prominently accelerated healing rate as shown by alleviating the excessive inflammatory, inducing efficiently proliferation, re-epithelialization, collagen deposition, and neovascularization. This work provides an effective strategy based on nanozyme-reinforced hydrogel as a ROS-driven oxygenerator for enhancing diabetic wound healing.

Polymeric coating on ß-TCP scaffolds provides immobilization of small extracellular vesicles with surface-functionalization and ZEB1-Loading for bone defect repair in diabetes mellitus.

Repair of critical-size bone defects in patients with diabetes mellitus (DM) has always been a challenge in clinical treatment. The process of bone defect regeneration can be impaired by underlying diseases including DM, but the mechanism remains unclear. In bone tissue engineering, the integration of bionic coatings and bioactive components into basic scaffolds are common function-enhancing strategies. Small extracellular vesicles (sEVs) have been applied for cell-free tissue regeneration in the last few years. We previously reported that sEVs have flexible and easily-extensible potential, through modular design and engineering modification. The impairment of CD31hiendomucinhi endothelial cells (ECs) whose function is coupling of osteogenesis and angiogenesis, is considered an important contributor to diabetic bone osteopathy, and ZEB1, which is highly expressed in CD31hiendomucinhi ECs, promotes angiogenesis-dependent bone formation. Thus we believe these ECs hold much promise for use in bone regeneration. In addition, c(RGDfC) has been reported to be a highly-effective peptide targeting αvß3, which is highly expressed in the bone microenvironment. In this study, we developed a hyaluronic acid (HA)/poly-L-lysine (PLL) layer-by-layer (LbL) self-assembly coating on ß-TCP (ß-tricalcium phosphate) scaffolds providing immobilization of modularized engineered sEVs (with c(RGDfC) surface functionalization and ZEB1 loading) to facilitate bone defect regeneration under DM conditions. RNA-seq was used to explore possible molecular mechanisms, and the therapeutic effects of bone regeneration were systematically evaluated in vitro and in vivo. Our data demonstrated that this strategy could be very effective in promoting the repair of diabetic bone defects, by enhancing angiogenesis, promoting osteogenesis and inhibiting osteoclast formation.